Palermo is the largest and greenest barrio in Buenos Aires. And it is one of the city's most vibrant neighborhoods. Head to Palermo Viejo for hip restaurants, fashionable clubs and cutting-edge boutiques. A trip to the Buenos Aires Planetarium provides a peek at the southern sky. The Buenos Aires Botanical Garden, Japanese Garden and Zoo are three things green. They offer weary travelers a chance to chill and tykes a place to run and jump.